/Engine/Source/Runtime/Engine/Public/Rendering/SkeletalMeshLODImporterData.h
MeshDescription always contains color, normal and tangent data by default. Therefore, while iterating over the vertices, we check if at least one normal/tangent vector is not a zero vector and the color is not white, then we set the corresponding bHasNormals/bHasTangent/bHasVertexColors flags to true.
static [FSkeletalMeshImportData](API\Runtime\Engine\Rendering\FSkeletalMeshImportData) CreateFromMeshDescription ( const [FMeshDescription](API\Runtime\MeshDescription\FMeshDescription) & InMeshDescription )